Self-regulating turbine

ABSTRACT

An energy cascade which is preferably fed by solar energy is made from standard solar absorbers including Seebeck elements on the upper end thereof, a self-regulating turbine including a generator arranged downstream and Seebeck elements arranged on the turbine outlet, a heat exchanger for the secondary circuit, and regulating devices for controlling the inner pressure of the primary circuit. The turbine is matched to varying operating conditions by means of suitable measures: matching of the inlet channel, changing turbine blade length for radial turbines, electronic control of the current generated in the generator for rotational speed limitation and a Seebeck heat/current exchanger in the turbine outlet channel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. §120 of InternationalApplication No. PCT/DE2003/003607, filed on Oct. 30, 2003, which claimspriority from German No. 102 51 752.5, filed on Nov. 5, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a self-regulating turbine.

2. The Prior Art

DE 42 00 507 A1 discloses a turbine with very many geometricaladjustment possibilities. These possibilities include adjusting theblade wheel 3 a, the flow gap or its size and at the same time theturbine vane length 2 or turbine blade length, and the spiral 14 is notchanged automatically by the blade spring 9.

Automatic geometrical alterations are disclosed by the documents U.S.Pat. No. 3,149,820 and U.S. Pat. No. 4,540,337.

These documents represent only a selection from many known technicalsolutions.

The known design concepts have long experimented with the use ofvariable guide vanes in particular, in order to alter the incoming flowangle and the incoming flow speed.

The known forms of turbines, however, are disadvantageous in terms ofthe optimal efficiency during variable daily and seasonal loads and inpossible pulsed operation. On account of the essentially rigid geometryof the rotor disk, or rather the turbine vanes, the optimal efficiencyis achieved only twice a day when using an upstream solar absorber toproduce steam or hot gas. During the remainder of the time, the turbineworks uneconomically in the underloaded or overloaded region (see FIG.1).

Furthermore, when using a turbine downstream from a solar absorber onemust consider that the turbine geometry is designed for a mean optimalworking range, which is supposed to make optimal utilization of thedaily and seasonal variations. Hence, with traditional turbine geometry,the optimal working point will be set relatively low. As a result, atraditional turbine will work at least 90% of the available time at aconsiderable distance from optimal operating states in the underload oroverload range. In other words, the turbine will achieve a meanefficiency of only perhaps 25%, as compared to an available 70%.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a turbine whichadapts to the variable daily and seasonal load of a turbine inparticular and also to a possible pulsed operation, and which adapts theturbine geometry to an optimal efficiency.

More particularly, it is an object of the present invention to provide aself-adapting turbine with nearly constant rotary speed for variabletorque with a mass flow of 0.5 to 20.0 l/s between 0.2 MPa at the intakeside and 0.1 MPa at the exit side, wherein angle-adjustable guide vanesand/or rotor vanes could not be considered in view of the requiredrobustness and compact size of the turbine.

These and other objects are achieved, in accordance with the invention,by finding other suitable measures besides the possible use ofadjustable rotor vanes for adapting the turbine to changing operationalstates with large variances. The measures according to the inventioninvolve, in particular:

-   -   adapting the inlet channel of the turbine, as well as    -   a variable turbine vane length for radial turbines, as well as    -   electronic control of the current produced in the generator in        order to limit the speed after reaching the rated speed and the        rated voltage, as well as    -   a Seebeck heat/current exchanger in the turbine outlet channel.

Specifically, the stated purpose is achieved as follows:

In a first measure, given the steam or gas masses of varying size, onemust strive to change the cross section of the inlet channel so that thequantity of steam or gas arriving vertically at the particular inletedge of the turbine vane can be kept approximately in the same optimizedspeed range.

This objective is accomplished, according to the invention, in a firstembodiment by providing an inlet channel that does not have a constantlytapering, circular-invariant cross section, as in the case of exhaustturbochargers, for example, but instead a rectangular cross section, inwhich there is situated an elastic sealing band that is placed undertension and closes off the channel vertically. When the quantity ofsteam or gas is small and the inlet pressure is low, this pretensioningof the sealing band ensures a very tiny inlet gap; when steam or gasquantities are large and the pressure is higher, the channel opensspontaneously to the maximum gap width, and the sealing band liesagainst the outer surface of the inlet channel at maximum opening.

A second solution according to the invention is one in which the inletchannel is closed off by an adjustable-height, suitably shaped andspring-loaded lid, so that the channel cross section can likewise beadapted to the particular load condition.

A third solution according to the invention is to use an elasticmaterial, suitable to the temperature and pressure range, to form thewall of an inlet channel; this expands as the pressure increases andthus forms a circular, constantly tapering cross section which isoptimal at all times.

In a second measure, because of the variable gas or steam quantitiesarriving at approximately the same speed thanks to the adjustable crosssection of the inlet channel, it proves to be advantageous to have theturbine vane of variable length, whereby a portion of the turbine vanescan be retracted into a cylindrical body rotating at the same speed,with negative shapes designed to accommodate the turbine vanes, and thisco-rotating body can close off the inlet region of the turbine vanes ormake it partly or fully open.

A comparable measure can be achieved at the turbine outlet by againhaving a co-rotating cylindrical body, in which the exit ends of theturbine vanes can be retracted such that the exit region can be largelyclosed off or fully opened up.

The co-rotating cylindrical body can have negative shapes on both sidesto accommodate the particular turbine vanes, and a central bore in themiddle for the fluid to flow through. The co-rotating cylindrical bodycan be fashioned as an impeller, in which the guide channel is bladed.

The first and second measures mentioned above have the effect that theturbine, automatically adjusting to different load conditions, quicklyreaches its rated speed even when the steam or gas mass flows are slightand the generator connected to the turbine likewise quickly reaches itsrated voltage. A limiting of the turbine speed is achieved in that thecurrent flow through the generator is steered by a suitable,voltage-dependent control system and the increasing current flowpresents a suitably high electromagnetic moment in opposition to theturbine torque.

The outer wall of the turbine outlet channel allows for heat to passthrough Peltier elements to a cooling channel, where the working fluidof the secondary circuit flows before going to the heat exchanger. Thismeasure makes possible a further recovery of current at the preferredtemperature difference of 150° C. to 30° C.

The automatically adjusting turbine should preferably be used forcurrent production with solar absorbers, but it can equally be used forother operating purposes with changeable loads. Given a suitable choiceof material, an operation with hot gas from combustion processes is alsopossible.

When used with solar absorbers, additional necessary devices whichcomplement the invention are specified for an optimal operation of thesolar absorber in dependence on the solar radiation.

Thus, the solar absorber at the upper end of the housing should beoutfitted with a Peltier heat/current exchanger. The warm side of theexchanger closes off the solar absorber housing at the inside. The outerside of the exchanger is shaded and subjected to forced thermalventilation and, thus, cooled.

Moreover, a heat exchanger is provided downstream from theturbine-generator set, which cools the particular selected working fluiddown to the absorber inlet temperature and furnishes the thermal energyrecovered from the exchanger to a heating circuit or a heat reservoir,for example.

In this case, the working fluid can be a gas or a liquid that isevaporated in the absorber and condensed back in the heat exchangercoming after the turbine.

The desired direction of work of the working fluid is ensured by a checkvalve at the lower inlet of the working fluid into the solar absorber,which only allows a flow into the absorber from underneath.

The absorber tubes lying in or on the absorber surface can be filledwith a good gas or steam-permeable and good heat-conducting fillermaterial, such as copper wool, in order to achieve a better transfer ofheat from the absorber surface through the wall surface of the absorbertube to the working fluid being heated. The absorber tube can also be anextruded hollow profile with individual star-shaped sections, in orderto present the largest possible heat transfer surface.

Moreover, when using an evaporating working fluid, it is advantageous tohave a variable inner pressure of the device in the absorber tubes inorder to produce an optimal steam quantity depending on the processtemperature which can be achieved in accordance with the solarradiation. Thus, water at normal pressure would evaporate only at 100°C., whereas familiar refrigerants do so at around 50° C. The innerpressure in the primary circuit should be coordinated with the flowtemperature of the secondary circuit so that the working fluid in theprimary circuit is exposed to a pressure whose corresponding boilingpoint is more than 5° C. above the flow temperature of the secondarycircuit.

This variable inner pressure is accomplished by an automatic device inwhich the interior of the absorber tubes is connected to a pressureregulating body, which is connected to the working fluid of thesecondary circuit via a membrane not permeable to gas or steam. At lowflow temperatures, the membrane is stretched by a bimetallic spring and,thus, the pressure is reduced inside the evaporation device.

It proves to be especially advantageous to operate the system in pulsedmode in the case of efficiency-critical low working temperatures and lowgas or steam quantity per unit of time, in that the absorber tubes arebrought together in a collective absorber tube and this collectiveabsorber tube only opens by a spring-loaded check valve at a presetpressure and the quantity of gas or steam produced by the energy inputis presented to the turbine in a pulse. This pulsed mode can be smoothedout by opening up two or more collective absorber tubes for admission tothe turbine in alternation.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the present invention will become apparentfrom the following detailed description considered in connection withthe accompanying drawings. It should be understood, however, that thedrawings are designed for the purpose of illustration only and not as adefinition of the limits of the invention.

In the drawings, wherein similar reference characters denote similarelements throughout the several views:

FIG. 1 is a graph showing efficiency of geometrically rigid turbines;

FIG. 2 shows a first embodiment of a turbine with axial inlet flow andradial outlet flow;

FIG. 3 shows the turbine embodiment of FIG. 2 with retractable turbinevanes;

FIG. 4 shows an embodiment of a turbine with a radial inlet and outletflow;

FIG. 5 shows a configuration of the radial inlet channels;

FIG. 6 shows blading of the inlet, middle, and outlet parts of anembodiment of the turbine;

FIG. 7 is a system view of a coupled solar absorber with a turbineaccording to an embodiment of the invention;

FIGS. 8-12 depict an opened housing of a turbine and the rotor indifferent positions in respect to a counter-housing in which the rotorcan be moved in to enlarge or to reduce the active area of the turbineblades;

FIG. 13 is a cross-sectional view of an embodiment of a turbine showingone type of construction for varying the active blades of the turbinerotor;

FIG. 14 shows an embodiment of the invention with the rotor moved to aposition different from that shown in FIG. 13;

FIG. 15 shows a rotatable control cylinder;

FIG. 16 shows an embodiment of the turbine with retractable turbinevanes moving against a spring action in accordance with another type ofconstruction; and

FIG. 17 is a perspective exterior view of the embodiment of FIG. 13.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In one aspect, a turbine is provided with an axial inlet flow and radialoutlet flow according to an embodiment of the invention. The turbine isdesigned for operation with varying gas or steam quantities at varyingtemperatures or pressures. The flow gap is closed after reaching therated speed in dependence on the available heated gas or steam quantityor the size of the flow gap between the turbine vanes and/or the turbineblade inclination and/or the length of the turbine vanes isautomatically adjusted as a function of pressure and/or temperature andthe change in current flow in the generator connected downstream fromthe turbine is used as an additional regulating quantity for limitingthe speed of the turbine.

Referring now in detail to the drawings, FIGS. 2 and 3 show a turbine inwhich several turbine sets 1 with an axial gas or steam borehole 2 arearranged axially to each other. Each turbine set 1 is arranged on aseparating seating disk. In the central gas or steam borehole a controlcylinder 3 loaded with a temperature and pressure-controlled springforce automatically opens up one, several, or all turbine sets dependingon the gas or steam quantity.

As shown in FIG. 4, one or more turbine stators 4 and turbine rotors 5of a turbine set may be arranged intermeshing in a plane. The availablegap in the rotational plane is automatically regulated by a temperatureand pressure-controlled spring force, depending on the quantity of gasor steam.

The turbine blade may be fastened from an elastic material so that, whengas or steam quantities are low, the tip of a turbine blade liestangentially against the neighboring blade with only a small outlet gap.As the gas or steam quantity increases the turbine blade isspontaneously deformed so that a larger gap is opened up with a smallerangle of attack of the turbine blade.

The turbine outlet channel may be configured variably thanks to atemperature and/or pressure elastic leaf spring 26, so that when gas orsteam quantities are low only a slight outlet gap is opened up. Whensteam or gas quantities are larger, the leaf spring is simultaneouslydeformed so that a larger outlet gap is opened up in the turbine outletchannel.

FIG. 3 shows a turbine with retractable turbine vanes, including animpeller 6 with turbine vane holders, and a spring 9 for pretensioning arotation body against impeller 6. When the turbine inlet flow is radial,the turbine vane segments running from outside to inside between theturbine blades in a first segment of the channel can be retracted in anegative form co-rotating axially as an impeller 6 and change after astreamlined central flow channel of the impeller into a last segment inwhich the turbine blades running from inside to outside can again beretracted into the negative shape.

FIG. 4 shows a turbine with radial inlet and outlet flow including aturbine inlet rotation body 7 with turbine vanes, a turbine outletrotation body 8 with turbine vanes, and a Peltier heat/current exchangeror Seebeck elements 14 at the turbine outlet channel. A Peltierheat/current exchanger takes advantage of the Peltier effect in whichcurrent flow across a thermoelectric junction produces cooling orheating. Seebeck elements take advantage of the Seebeck effect in whichcurrent will flow when two dissimilar conductors are made into a circuitso long as the junctions are at different temperatures. As shown in FIG.4, the two rotation bodies 7, 8 carrying the turbine vanes form, withthe negative shape accommodating the turbine vanes in the shape of animpeller, a structural assembly that is pretensioned by one or moresprings 9 so that when gas or steam flows are increasing the turbinevanes are partly or entirely opened up.

The inlet channel may be configured with a tapering profile and can beadapted, as a function of load, to the conditions of usage by an inletchannel variable height profile 10 shown in FIG. 4 or an inlet channelvariable depth profile 11 shown in FIG. 5. This adaptation is achievedby springs 12 which are tensioned. Tensioning springs 12 are shown inFIGS. 4 and 5 for the height or depth profile respectively.

FIG. 6 shows blading of the inlet, middle, and outlet parts of theturbine including a profile with a wall 13. The inlet channel, which isconfigured with a tapering profile, may have a cross-sectional profilevarying as a function of load. Wall 13 of the profile may be made of apressure-sensitive, elastic material.

The turbine and the generator may be connected downstream to a heatexchanger 16 which cools the working fluid of a first circuit andprovides the heat recovered in this way to a second circuit.

The outer wall of the turbine outlet channel may have Seebeck elements14. The outer side of the Seebeck exchanger is formed by a coolingchannel 15 through which the working fluid of a secondary circuit flowsbefore entering the heat exchanger 16.

FIG. 7 shows a system view of a solar absorber coupled with a turbinehaving a downpipe 17 to an absorber inlet, a pressure regulating vessel20 having a bimetallic controlled membrane 21, and a Seebeckheat/current exchanger element 25 on the absorber. As shown in FIG. 7,the turbine with generator and the heat exchanger in the first circuit,after downpipe 17 with a check valve or valves 18 closing it off, arefollowed by one or more absorber tubes 19 in an ascending absorber forincoming thermal energy, including solar energy, which supply hot gas orsteam to the turbine.

An evaporable liquid or a gas may be used as the working fluid in thefirst circuit. Preferably, a working fluid which boils at lowtemperatures is used. For such boiling, the pressure in the firstcircuit can be lowered to the suitable low boiling temperature with morethan 5 degrees Kelvin above the flow temperature of the heat exchanger16 by self-regulating vessel 20 with bimetallic membrane 21.

The heater tubes, for better transfer of heat to the working fluid, maybe additionally outfitted with good heat-conducting and gas orsteam-permeable filler bodies 22. The heater tubes may also be extrudedprofiles having individual flow channels separated by ridges.

Two or more absorbers may be alternately admitted to the turbine inpulsed mode or smoothed pulse mode across collective absorber tubes 23.The pulse operation is preferably regulated by coupled, pretensionedcheck valves 24 on the collective absorber tubes.

Either a rotating turbine base plate at the side away from the turbinevanes or the rotating impeller on its outside may have permanent magnetsof alternating polarity. The excitation windings of the generator may bearranged opposite the rotation gap.

The absorbers may be closed off by Seebeck elements at the upper end ofthe housing which are directly shaded and under forced air cooling fromthe outside.

FIGS. 8-12 show an opened housing of an embodiment of the turbine andthe rotor in different positions in respect to a counter-housing inwhich the rotor can be moved in to enlarge or to reduce the active areaof the turbine-blades.

In FIG. 8, the blades are quite small as shown on the right hand sidethereof. The blades are larger in FIG. 9 and larger in FIG. 10. FIG. 11is a side view of the turbine-blades with the blades being quite large.In FIG. 12, the blades just dive in the right hand side rotatablecounter-part.

FIG. 13 shows turbine housing 30 in which a turbine wheel, i.e. turbinerotor 5, is shifted against a spring 31 for movement deeper and deeperinto a rotatable control cylinder 3. FIG. 15 shows control cylinder 3 inmore detail and FIG. 17 shows a tiny portion of control cylinder 3.

Input channels and output channels are designated with referencenumerals 32 and 33 in FIG. 13. A generator 34 is shown within housing 30but may be outside housing 30 on the rotary shaft 35 of the turbinerotor 5 and the control cylinder 3.

In order to cause axial movement of turbine rotor 5, turbine rotor 5 isfixed on a part of shaft 35 which is, for example, quadratic in itssquare area. See FIG. 13.

In accordance with the invention, there are at least two different typesof constructions that can be used to vary the area of the active bladesof the turbine. One form of construction is shown in FIGS. 13 and 17(and FIGS. 8-12) where the turbine rotor moves in and out of controlcylinder 3. Another possibility is shown in FIG. 16 where controlcylinder 3 moves against a spring action and is shown also in FIG. 3.

Although only a few embodiments of the present invention have been shownand described, it is to be understood that many changes andmodifications may be made thereunto without departing from the spiritand scope of the invention as defined in the appended claims.

1. A turbine for operating with varying gas or steam quantities atvarying temperatures and pressures comprising: (a) a plurality ofturbine vanes, each turbine vane having a length; (b) a plurality ofturbine blades, each turbine blade having a turbine blade inclination;and (c) a flow gap having an adjustable size arranged between saidturbine vanes; wherein said flow gap is closed after the turbine reachesa rated speed in dependence on an available heated gas or steam quantityor the size of the flow gap or the turbine blade inclination or thelength of the turbine vanes or a combination thereof is automaticallyadjusted as a function of pressure or temperature or both and a changein current flow in a generator connected downstream from the turbine isused as an additional regulating quantity for limiting turbine speed. 2.The turbine according to claim 1 further comprising: (a) a plurality ofturbine sets arranged axially to each other having an axial gas or steamborehole, each turbine set arranged on a respective separating sealingdisk; (b) a control cylinder provided in a central gas or steam inletborehole; (c) a temperature and pressure-controlled spring biasing saidcontrol cylinder with a temperature and pressure-controlled spring forceto automatically open at least one of said turbine sets depending on aquantity of gas or steam.
 3. The turbine according to claim 1 whereineach turbine set comprises at least one stator and at least one rotorarranged to interact in a plane and an available gap in a rotationalplane is automatically regulated by a temperature andpressure-controlled spring force, depending on a quantity of gas orsteam.
 4. The turbine according to claim 1 wherein each turbine bladehas a tip and said turbine blades are made from an elastic material sothat when a quantity of gas or steam is below a selected amount, the tipof a respective turbine blade lies tangentially against a neighboringblade with an outlet gap below a selected size and as the quantity ofgas or steam increases above the selected amount the turbine blade isautomatically deformed so that the size of the outlet gap increases witha decreased angle of attack of the turbine blade.
 5. The turbine bladeaccording to claim 1 further comprising a turbine outlet channel havinga variable outlet gap dimension and a temperature or pressure-elasticleaf spring varying the outlet gap dimension so that when a quantity ofgas or steam is below a selected amount, the outlet gap dimension isbelow a selected size and when the quantity of steam or gas is above theselected amount, said leaf spring is automatically deformed so that theoutlet gap dimension increases above the selected size.
 6. The turbineblade according to claim 1 wherein the turbine vanes have retractableturbine vane segments and the turbine has a flow channel comprising afirst segment, a streamlined central flow segment, and a final segment,and wherein when turbine inlet flow is radial, the turbine vane segmentsrunning from outside to inside in the first segment of the channel canbe retracted to a withdrawn form axially co-rotating as an impeller andchange after the streamlined central flow segment in the final segmentin which the turbine blades running from inside to outside can again beretracted into the withdrawn form.
 7. The turbine according to claim 1further comprising: (a) a structural assembly comprising at least tworotation bodies carrying the turbine vanes and an impeller accommodatingthe turbine vanes; and (b) at least one spring pretensioning saidstructural assembly so that when gas or steam flow increases, theturbine vanes at least partially open up.
 8. The turbine according toclaim 6 wherein said flow channel comprises an inlet channel having atapering profile, said inlet channel being adaptable as a function ofload to varying operating conditions by a plurality of tensioningsprings and a variable height profile or a variable depth profile. 9.The turbine according to claim 6 wherein said flow channel comprises aninlet channel having a tapering profile, said inlet channel comprising across-sectional profile having a wall made from a pressure-sensitive,elastic material that varies as a function of load.
 10. A turbineaccording to claim 6 further comprising: (a) a heat exchanger; (b) asecondary circuit; and (c) Seebeck elements having an outer side formedby a channel through which working fluid of the secondary circuit flowsbefore entering the heat exchanger; wherein said flow channel comprisesa turbine outlet channel having an outer wall, said outer wall havingsaid Seebeck elements.
 11. A turbine assembly comprising a turbine foroperating with varying gas or steam quantities at varying temperaturesand pressures, a generator arranged downstream from said turbine, and aheat exchanger arranged downstream from said turbine and said generator,said heat exchanger cooling working fluid of a first circuit andproviding recovered heat to a second circuit, wherein said turbinecomprises: (a) a plurality of turbine vanes, each turbine vane having alength; (b) a plurality of turbine blades, each turbine blade having aturbine blade inclination; and (c) a flow gap having an adjustable sizearranged between said turbine vanes; wherein said flow gap is closedafter the turbine reaches a rated speed in dependence on an availableheated gas or steam quantity or the size of the flow gap or the turbineblade inclination or the length of the turbine vanes or a combinationthereof is automatically adjusted as a function of pressure ortemperature or both and a change in current flow in the generator isused as an additional regulating quantity for limiting turbine speed.12. A turbine assembly comprising a turbine for operating with varyinggas or steam quantities at varying temperatures and pressures, agenerator arranged downstream from said turbine, and a heat exchanger ina first circuit, wherein said turbine and said generator and said heatexchanger, after a downpipe with a check valve for closing the downpipe,are followed by at least one absorber tube in an ascending absorber forincoming thermal energy, including solar energy, said at least oneabsorber tube supplying hot gas or steam to the turbine, wherein saidturbine comprises: (a) a plurality of turbine vanes, each turbine vanehaving a length; (b) a plurality of turbine blades, each turbine bladehaving a turbine blade inclination; and (c) a flow gap having anadjustable size arranged between said turbine vanes; wherein said flowgap is closed after the turbine reaches a rated speed in dependence onan available heated gas or steam quantity or the size of the flow gap orthe turbine blade inclination or the length of the turbine vanes or acombination thereof is automatically adjusted as a function of pressureor temperature or both and a change in current flow in the generator isused as an additional regulating quantity for limiting turbine speed.13. The turbine assembly according to claim 11 wherein the working fluidin the first circuit comprises an evaporable liquid or a gas.
 14. Theturbine assembly according to claim 11 further comprising aself-regulating pressure vessel with a bimetallic membrane, wherein theworking fluid comprises a liquid that boils at a low boiling temperatureand said self-regulating pressure vessel lowers pressure in the firstcircuit so that the low boiling temperature is more than 5 degreesKelvin above flow temperature of said heat exchanger.
 15. The turbineassembly according to claim 12 wherein said at least one absorber tubecomprises a plurality of heater tubes provided with heat-conducting andgas or steam-permeable filler bodies or formed as extruded profileshaving individual flow channels separated by ridges for improvedtransport of heat to the working fluid.
 16. The turbine assemblyaccording to claim 12 further comprising a plurality of collectiveabsorber tubes having coupled predetermined check valves, wherein saidabsorber comprises at least two absorbers alternately admitted to theturbine in pulsed mode or smoothed pulse mode across said collectiveabsorber tubes, said coupled, pretensioned check valves regulatingpulsed operation of said at least two absorbers.
 17. The turbineassembly according to claim 11 further comprising permanent magnets ofalternating polarity, said permanent magnets being provided on either arotating turbine base plate at a side away from the turbine vanes or anoutside of a rotating impeller, wherein the generator has excitationwindings arranged opposite a rotation gap.
 18. The turbine assemblyaccording to claim 16 further comprising a housing and Seebeck elementsat an upper end of said housing, said Seebeck elements closing off saidabsorbers and being directly shaded and under forced air cooling on theoutside.